I've been surprised at how very little RM has changed over the years.
We use a lot of the old MERP modules for RMFRP and the conversions are easy enough.
Even the really old stuff in RoCo's (Rolemaster Companions) is easy enough to convert.
Everyone has points they like/dislike. YGMV.
Just a few examples:
1) The old stat bonus system was easier (+5 progression), but I like how you get smaller bonuses at lower stats in RMFRP.
2) The separation of spell types was a good addition, too. For the most part, it's clear how spells interact with the game world.
3) Skill Cat's make sense to me. I don't wan't to lose those.
If the new system maintains RAW that I don't like, then that's easy to convert as well. I don't use it.
1) Penalties for PP exhaustion. Being low on PP is bad enough.
2) +50 Artifact weapons (crazy over the top example) is trumped by your riding skill..
3) Clean up poor example so they are pertinent to the the current rules. Don't assume
otherwise intelligent people understand the cut and paste editing that may no longer apply.
4) DP based on stats. This is a carryover from bonus xp from high stats in D&D. Having higher stats is bonus enough.
I looked at some of the D&D versions over the years and I didn't understand why you basically had to learn an entirely new game just to play. IMHO.
In all it's incarnations, I don't feel RM was ever that negligent to it's fan base.